Here's why your mouth might get itchy or tingly when you eat fresh fruits and veggies

White House PhotoPresident Barack Obama eats a peach following a town hall meeting at Kroger’s Supermarket in Bristol, Va. on July 29, 2009.

It started after a bite of a peach one summer.

I was in high school, and I’d never had an allergic reaction. But here I was, just trying to enjoy some late-summer fruit — instead, the back of my throat felt itchy and my lips were swollen.

Soon I realised I had the same experience with carrots, apples, pears, cherries and on occasion, almonds.

The surprising culprit: a seasonal allergy to pollen that manifests itself in some of the raw foods I ate. It’s called oral allergy syndrome.

The most common symptoms of oral allergy syndrome, according to the American Academy of Allergy Asthma and Immunology, are an itchy mouth along with swelling of the lips, mouth, throat, face, and tongue. Dr. Jacqueline Pongracic, head of allergy and immunology at the Ann and Robert H. Lurie Children’s Hospital of Chicago told Business Insider that she sees cases of oral allergy syndrome (also called pollen allergy syndrome) regularly, though there aren’t really any good numbers on how many people nationally have it.

According to the Mayo Clinic, it occurs when people get sensitive to an environmental allergen, like certain pollen coming off trees and grasses. Then, when they eat a food that contains a closely-related protein, they have a reaction. Birch pollen, in particular, is a big culprit — it has a protein that’s similar to a number of proteins present in fruits and nuts.

The reactions tend to pop up in late teens or early adulthood, after people have gone years eating certain fruits without a problem. This is different from traditional food allergies, like milk and peanuts, that tend to pop up in young children.

Here’s a chart that maps out which pollen are related to which allergic reactions

Pongracic also says that oral allergy syndrome could pop up when eating some herbs, seeds, and even some nuts.

How to avoid a reaction

The Mayo Clinic notes the proteins that people react to tend to break down when they’re cooked (which could be all the more reason to bake a peach or apple cobbler). Reactions could also differ based on what season it is, with possibly wors reactions happening after a pollen season.

Pongracic said that while most people suffering from oral allergy syndrome don’t necessarily bring it up with their doctors, it’s helpful to let them know, so they can keep a record of what’s going on. That’s especially important for people who have reactions to cooked fruit, or who have reactions to certain foods but don’t have seasonal allergies. That could be a sign of a food allergy.